1. Field of the Invention
The present invention relates to an electronic component for use in an electronic circuit in the communication field such as a portable telephone or a television, which includes at least one piezoelectric vibrating-portion and a connecting portion provided on a substrate.
2. Description of the Related Art
The basic structure of such electronic components includes a piezoelectric vibrating-portion provided on a substrate, which is accommodated in a package providing an air tight seal, in order to ensure its reliability.
A portion of the package corresponding to the upper surface of the piezoelectric vibrating portion includes a space such that the vibration of the piezoelectric vibrating portion provided on the substrate is not disturbed. A package made of a metal or ceramic is used to ensure the reliability. However, the above-described structure increases the size of the package. This prevents size reduction of electronic components.
Moreover, the substrate must be provided with an electrical connection for input-output, in order to realize the characteristics of the piezoelectric vibrating portion formed thereon. To provide such an electrical connection, a connecting portion provided on the substrate and another desired connecting portion are electrically connected via a wire or a bump. However, this increases the size of the electronic component.
The following electronic component is disclosed (e.g., see Japanese Unexamined Patent Application Publication No.1996-330894 (Patent Document 1)). In a surface acoustic wave device having a piezoelectric substrate including components disposed thereon, the piezoelectric substrate and a glass member having a space to permit vibration of the surface acoustic wave with the thermal-expansion-coefficient in conformity to that of the piezoelectric substrate, are anode-joined to each other, and are sealed. Moreover, a through hole is provided in the glass member such that the piezoelectric substrate is electrically connected to the outside. Thus, the electronic component itself defines a package base.
However, the above-described electronic component including the piezoelectric substrate sealed with a glass member has the following problems. According to Patent Document 1, in order to seal an IDT electrode provided on the piezoelectric substrate, the glass member, having a space provided on the upper portion of an IDT electrode so as not to disturb the vibration, is anode-joined to the piezoelectric substrate. However, generally, piezoelectric substrates have a high insulating property. Thus, for application of an electronic field, it is necessary to provide an electroconductive member on the joining portions. Therefore, a wiring can not be provided in the joining portions. Thus, the size of electronic component cannot be sufficiently reduced.
Moreover, the glass member must have a thermal expansion coefficient that is equal to that of the piezoelectric substrate. Thus, glass members including moving ions such as lithium ions, sodium ions, or other ions are used. The moving ions have corrosive action on electrode materials such as Al. Thus, the moving ions greatly reduce the reliability of electronic component.
As a method of forming a space in the glass member, a metal is formed into a mask by sputtering or other suitable method, and is etched with hydrofluoric acid or other suitable etching substance to form a space. These processes greatly increase the manufacturing costs.
Moreover, an electrochemical discharge-drilling technique or a supersonic wave drilling technique is used to form the through hole in the glass piece. This technique is limited with respect to the size of the through hole to be formed, cannot be used in mass production, and is expensive.
Moreover, the glass piece is likely to be cracked or broken during the through processing of a wafer because of the low mechanical strength of the glass piece. When the above-described structure is used, the thickness of the sealing cap must be reduced to reduce the height of the electronic component. However, when the thickness of the sealing cap is reduced, the mechanical strength of the sealing cap is reduced. Thus, the sealing cap is often broken during the manufacturing process.